Earthquake Hazard and Safety (back to to homepage)

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Vocabulary

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liquefaction-only occurs when the shaking of an earthquake suddenly makes loose soft soil into liquid mud
aftershock- a smaller earthquake that occurs after a larger earthquake
tsunami- a huge wave caused by underwater earthquakes
base-isolated building- a structure that is mounted on bearings designed to take up the energy of an earthquake

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Outline

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• How Earthquakes Cause Damage
  • S waves cause severe damage to the epicenter
  • S waves put enough force to tear buildings apart
• *Local Soil Conditions*
  • when seismic waves move from hard soil to soft soil, they transmit their energy
  • the loose soil shakes more than the surrounding rocks
  • the thicker the soil, the more violent the shaking will be
• *Liquefaction*
  • the process that changes loose soil into liquid mud
  • can trigger land slides
• *Aftershocks*
  • occurs after bigger earthquake
  • may strike minutes, hours, days, and even months later
• *Tsunami*
  • underwater earthquakes
  • spreads out to the ocean from Earth's epicenter
  • the distance between wave of tsunami is 100~200 kilometers
• Making Buildings Safer
  • must be flexible and strong
  • older building s must be modified to withstand stronger quakes
• *Choice of Location*
  • steep slope pose to the danger of landslides
  • filled land shakes violently
  • should avoid building structures near fault lines
  • the farther from the fault the building is, the less it will shake during a quake
• *Construction Methods*
  • brick and wood framed buildings may collapsed if not reinforced
  • sometimes plywood sheets are used for reinforcement
  • new houses built on soft ground should be anchored to solid rock beneath soil
  • use base-isolation bearings to absorb energy of earthquake
• Protecting Yourself During an Earthquake
  • best way is to drop, cover, hold**
  • crouch beneath sturdy table so it doesn't slide away and hit someone
  • desk or table will provide protection for the head
  • if no desk, crouch against inner wall
  • if outdoors, avoid vehicles, trees, power lines,trees and buildings especially ones with brick chimneys or brick walls----

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